Characteristics and variety of living organisms — Edexcel International GCSE Science (Double Award)
The characteristics of living organisms, and the features of plants, animals, fungi, protoctists, bacteria and viruses.
Revision notes
5 short notes, in the order of the specification. Each one in short:
Living organisms are things that show all eight characteristics of life: nutrition, respiration, excretion, response to surroundings, movement, control of internal conditions, reproduction, and growth and development. Plants and animals show them in different ways. For example, a plant moves by growing towards light and makes its own food by photosynthesis, while an animal eats.
Plants and animals are multicellular eukaryotic organisms, so their cells have a nucleus. Plant cells contain chloroplasts, have cellulose cell walls, carry out photosynthesis and store carbohydrate as starch or sucrose. Animal cells have no chloroplasts or cell walls, animals often store carbohydrate as glycogen, and they usually have nervous co-ordination and can move from place to place.
Fungi are eukaryotic organisms that cannot photosynthesise. Most are made of thread-like hyphae forming a mycelium, have cell walls made of chitin and feed by saprotrophic nutrition: they secrete digestive enzymes onto food outside the body and absorb the products. Protoctists are microscopic single-celled eukaryotes, such as Amoeba, Chlorella and Plasmodium, which causes malaria.
Bacteria are microscopic, single-celled prokaryotic organisms with no nucleus. A bacterial cell has a cell wall, cell membrane and cytoplasm, and its DNA is a circular chromosome found free in the cytoplasm, along with small rings of DNA called plasmids. Lactobacillus bulgaricus is used to make yoghurt, while Pneumococcus is a pathogen that causes pneumonia.
A pathogen is an organism or particle that causes disease, such as a fungus, bacterium, protoctist or virus. Viruses are not living organisms: they are particles smaller than bacteria, with no cellular structure, a protein coat and one type of nucleic acid, DNA or RNA. They are parasitic and can reproduce only inside living cells.
Exam questions
7 exam-style questions (21 marks), each with its mark scheme.
Answer the questionsFlashcards
22 cards: flip them, mark what you knew, and practise the rest.
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The whole of the nature and variety of living organisms on one page, so you can see where this subtopic fits.
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Quick check questions
Give any four characteristics shared by all living organisms.
Show answer
Any four from: nutrition, respiration, excretion, response to surroundings, movement, control of internal conditions, reproduction, growth and development.
What are fungal cell walls made of?
Show answer
Chitin.
What is the name for the thread-like structures that make up a fungal mycelium?
Show answer
Hyphae.
Give two features of a bacterial cell.
Show answer
Any two from: cell wall, cell membrane, cytoplasm, plasmids, circular chromosome of DNA, no nucleus.
Why are viruses not classed as living organisms?
Show answer
They have no cellular structure and can reproduce only inside living cells.
Frequently asked questions
What are the eight characteristics of living organisms?
The eight characteristics are nutrition, respiration, excretion, response to surroundings, movement, control of internal conditions, reproduction, and growth and development. All living organisms show every one of them, although in different ways. A plant, for example, moves by growing towards light, while an animal can move from place to place.
What is the difference between excretion and egestion?
Excretion is removing the waste products made by chemical reactions in cells, such as carbon dioxide. Egestion is removing undigested food from the gut. Only excretion is one of the characteristics of living organisms, so in an exam do not use the two words as if they mean the same thing.
What is the difference between prokaryotic and eukaryotic cells?
Prokaryotic cells, such as bacteria, have no nucleus: their DNA is a circular chromosome free in the cytoplasm, often with extra rings called plasmids. Eukaryotic cells, found in plants, animals, fungi and protoctists, have their DNA enclosed in a nucleus. Bacteria are also microscopic and single-celled, while many eukaryotes are multicellular.
How do fungi feed?
Fungi feed by saprotrophic nutrition. They secrete digestive enzymes onto food material outside their body, which is called extracellular secretion, and then absorb the small organic products that are released. Fungi cannot photosynthesise, so they rely on this way of feeding, and they may store the carbohydrate they gain as glycogen.
Why are viruses not considered living?
Viruses are not considered living because they have no cellular structure and can reproduce only inside living cells. A virus is just a particle with a protein coat around one type of nucleic acid, either DNA or RNA. Examples include the tobacco mosaic virus, the influenza virus and HIV, which causes AIDS.
Written and checked against the Edexcel IGCSE Science Double Award (4SD0) specification · Updated October 2026